1. Technical Field
The embodiments herein generally relate to wireless communication systems, and, more particularly, to coarse frequency offset estimation in wireless communication systems.
2. Description of the Related Art
Orthogonal Frequency Division Multiplexing (OFDM) is a digital multi-carrier modulation scheme, which uses a large number of closely-spaced orthogonal sub-carriers. OFDM, because of its multiple advantages (e.g., high spectrum efficiency, resistance against multi-path interference, and ease of filtering out noise, etc.), has been widely used in wireless transmission technology such as terrestrial digital broadcasting. In a digital broadcasting receiver design such as Integrated Services Digital Broadcasting-terrestrial (ISDB-T) and Integrated Services Digital Broadcasting—terrestrial digital sound broadcasting (ISDB-TSB), the major disadvantage for OFDM systems is its impairment due to coarse frequency offset.
Frequency offsets usually arise due to mismatched transmitter and receiver oscillators. The occurrence of a coarse frequency offset in the receiver causes a difference in the locations of the received data and control bins which are different from locations specified by the corresponding OFDM system standards. The location difference indicates the presence of coarse frequency offset. Hence, it is needed to estimate the coarse frequency offset and compensate it before receiving and decoding the received data. In an ISDB-T or ISDB-TSB OFDM symbol, there are data bins, pilot bins, transmission and multiplexing configuration control (TMCC) bins, and auxiliary channel (AC) bins.
The transmitted power on pilot, TMCC, and AC bins are 2.5 dB higher than that on the data bins. An approach for coarse frequency offset estimation based on the raised power property of pilot, TMCC, and AC bins is generally not reliable, especially when the channels are noisy and dynamic and there are echoes. In order to have an estimate of the coarse frequency offset before receiving and decoding the received data, a more reliable approach is desirable.